1. Field of the Disclosed Embodiments
This disclosure relates to systems and methods for implementing more consistent vacuum belt transport movement for the transport of image receiving media in image forming devices, and for the transport of packages and components for processing and storage in myriad transport belt systems employing vacuum plenums to support and secure the materials being transported on the vacuum belts.
2. Related Art
Many industries use component transport belt systems in order to transport individual packages, components and the like between and through package and/or component processing devices, or within, for example, warehouse structures for storage or delivery. The vacuum belts used in certain vacuum belt transport systems may be perforated with holes that facilitate the application of a vacuum pressure from one or more vacuum plenums located beneath the vacuum belt over at least a portion of the transport path traversed by the vacuum belt in the vacuum belt transport system. Such configurations are intended to aid in precisely and/or securely positioning and holding the individual packages, components and the like on the vacuum belt to support package and/or component processing, or to securely transporting individual packages, components and the like over at least a portion of the transport path of the vacuum belt transport system.
In image forming devices, such vacuum and vacuum-aided belt transport systems may be employed to precisely hold sheets of image receiving media, particularly large sheets of image receiving media, to a vacuum belt transport mechanism to support precise image forming and finishing operations in the image forming devices. In order to illustrate the precision required, consider image forming on a sheet of image receiving media using one or more stationary inkjet print heads as the marking unit in the image forming device. The sheet of image receiving media is translated past the one or more stationary inkjet print heads by the perforated vacuum belt to which the sheet of image receiving media is held in the vacuum belt transport system. In order to avoid mis-registration or other image quality errors, the movement of the sheet of image receiving media past the inkjet print head must be precisely controlled. A speed of movement of the sheet of image receiving media must be constant. Movement of the sheet of image receiving media cannot be accelerated, decelerated, or jittered based on random excursions in transport belt movement in the vacuum belt transport system.
Difficulties may arise as differing sizes, compositions and/or numbers of image receiving media substrates are transported on a vacuum transport belt in the image forming device. It can be well understood that, as numbers and sizes of image receiving media substrates to be transported by a vacuum transport belt are varied, overall vacuum pressures to which the vacuum transport belt/substrate combinations may be subjected, over at least a portion of the movement of the vacuum transport belt in the vacuum belt transport system, will vary. These varying vacuum pressures may introduce different levels of frictional force or frictional loading within the vacuum belt transport system. The vacuum belt, for example, may be differently pulled, under varying vacuum pressure forces, against underlying structural components within the vacuum belt transport system. Based on an elasticity, or flexibility, in the vacuum belt, the frictional forces introduced underneath the vacuum belt may cause the vacuum belt to randomly stretch and/or surge resulting in the random excursions in vacuum transport belt movement which may be detrimental to image quality in the produced images in the image forming device.
The resulting differing levels of frictional forces that may be introduced in this manner must be reasonably and/or completely compensated for with the vacuum belt drive components in the vacuum belt transport system. Such compensation may require, for example, complicated vacuum belt drive feedback solutions. Failure to provide detection of, and compensation for, such random excursions in vacuum transport belt movement will result in detrimentally adverse effects on the quality for the images formed on the image receiving media substrates transported by the vacuum belt transport system.
In the context of individual package transport within a factory, processing or warehouse facility over massive and/or extensive vacuum belt transport systems, it can be readily extrapolated from the above discussion that introduction of additional friction forces across portions of an expansive vacuum belt transport system may produce equally detrimental effects. Timing for individual packages or components reaching certain processing stations may be adversely affected. Timing for individual packages being delivered to output bins or stations may be equally adversely affected. Further, and somewhat more insidious, individual components within the vacuum belt transport system may be subject to differential and/or accelerated wear causing one or more of those individual components to prematurely fail, or to at least require more frequent replacement based on adverse effects on the life cycle of the individual components. While it is true that these effects may be mitigated by over-engineering such more expansive vacuum belt transport systems, there is a cost associated with that over-engineering as well.
Very simply described then, difficulties in vacuum belt transport systems can arise based on a number of physical factors. When transporting large media or multiple media items on a vacuum belt in a vacuum belt transport system, especially on longer vacuum belts, the normal forces created by the vacuum results is increased force between the back side of the vacuum belt and various underlying components including, but not limited to, the vacuum belt guides or guide structure. As more media is added to the vacuum belt, and/or the vacuum belt gets longer, or the sheets get larger, a vacuum belt to guide structure force continues to increase and causes several issues. This force drives up the frictional load on the vacuum belt, which then requires increased torque from the one or more drive motors in the vacuum belt transport system. Motion profiles are affected by the changes in load. Traditional elastomer vacuum belts tend to stretch under the increased loads. An example where such difficulties may particularly manifest themselves may be in systems in which individual vacuum belts are used as part of a parallel vacuum belt transport system. Uneven movement differentially introduced between the individual vacuum belts in the parallel vacuum belt transport system, based on individual vacuum belt deformation/stretch and/or frictional forces causing uneven motion profiles between the vacuum belts, will lead to differential vacuum belt timing issues and consequential skew in the products transported on the vacuum belts.
In summary, expansive vacuum belt transport systems may require additional power to compensate for the frictional forces introduced by vacuum loading across the expanse of the vacuum belt transport systems. Image forming devices may sacrifice image quality based on the frictional forces introduced by vacuum loading across the vacuum belt transport systems. Regardless of how the detrimental effects of frictional forces manifest themselves, productivity can generally be adversely affected in such vacuum belt transport related systems.